**************************************
GVP/USGS Weekly Volcanic Activity Report
25-31 October 2006
http://www.volcano.si.edu/reports/usgs/
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New Activity/Unrest: | Cleveland, Alaska | Mayon, Philippines
Ongoing Activity: | Bulusan, Philippines | Colima, México | Karymsky,
Russia | Kilauea, USA | Langila, Papua New Guinea | Rabaul, Papua New
Guinea | Sakura-jima, Japan | Santa María, Guatemala | Semeru, Indonesia
| Soufrière Hills, Montserrat | St. Helens, USA | Sulu Range, Papua New
Guinea | Suwanose-jima, Japan | Tungurahua, Ecuador | Ubinas, Perú
New Activity/Unrest
CLEVELAND Aleutian Islands, USA 52.82°N, 169.95°W; summit elev. 1,730 m
AVO raised the Alert Level for Cleveland from Advisory to Watch on 28
October based on pilot reports of an ash plume. Satellite imagery
confirmed the presence of a plume drifting ENE at an altitude estimated
at 6.1 km (20,000 ft) a.s.l. A pilot reported that the altitude of the
plume was in excess of 9.1 km (30,000 ft) a.s.l. On 30 October, the
Alert Level was lowered back to Advisory because of no further evidence
of activity.
Geologic Summary. The symmetrical Mount Cleveland stratovolcano is
situated at the western end of the uninhabited dumbbell-shaped
Chuginadak Island in the east-central Aleutians. The 1,730-m-high
stratovolcano is the highest of the Islands of Four Mountains group and
is one of the most active in the Aleutians. Numerous large lava flows
descend its flanks. It is possible that some 18th to 19th century
eruptions attributed to Carlisle (a volcano located across the Carlisle
Pass Strait to the NW) should be ascribed to Cleveland. In 1944
Cleveland produced the only known fatality from an Aleutian eruption.
Recent eruptions from Mt. Cleveland have been characterized by
short-lived explosive ash emissions, at times accompanied by lava
fountaining and lava flows down the flanks.
Source: Alaska Volcano Observatory http://www.avo.alaska.edu/
Cleveland Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1101-24-
MAYON southeastern Luzon, Philippines 13.257°N, 123.685°E; summit elev.
2,462 m
PHIVOLCS announced the lowering of the Alert status for Mayon from Alert
Level 2 to Alert Level 1 on 25 October. The 7-km Extended Danger Zone
(EDZ) on the SE flank remained in effect.
Geologic Summary. The beautifully symmetrical Mayon volcano, which rises
to 2,462 m above the Albay Gulf, is the Philippines' most active
volcano. The structurally simple volcano has steep upper slopes that
average 35-40° and is capped by a small summit crater. The historical
eruptions of this basaltic-andesitic volcano date back to 1616 and range
from Strombolian to basaltic Plinian. Eruptions occur predominately from
the central conduit and have also produced lava flows that travel far
down the flanks. Pyroclastic flows and mudflows have commonly swept down
many of the approximately 40 ravines that radiate from the summit and
have often devastated populated lowland areas. Mayon’s most violent
eruption, in 1814, killed more than 1,200 people and devastated several
towns. Eruptions that began in February 2000 led PHIVOLCS to recommend
on 23 February the evacuation of people within a radius of 7 km from the
summit in the SE and within a 6 km radius for the rest of the volcano.
Source: Philippine Institute of Volcanology and Seismology
http://www.phivolcs.dost.gov.ph/
Mayon Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-03=
Ongoing Activity
BULUSAN Luzon, Philippines 12.770°N, 124.05°E; summit elev. 1,565 m
PHIVOLCS reported that during 25-26 October, a lahar from Bulusan
deposited sediments 15 cm (6 in) thick along a tributary leading to the
Gulang-gulang River. According to news articles, the lahar mobilized
boulders as large as trucks and caused at least 96 people to evacuate.
During 30-31 October, ash explosions generated a light gray
ash-and-steam plume that rose to 2.3 km (7,400 ft) a.s.l. and drifted
NNE. Later field inspection revealed ashfall (trace to 1 mm) in the N
sectors of the volcano, including areas in the municipalities of
Casiguran and Gubat.
Geologic Summary. Luzon's southernmost volcano, Bulusan, was constructed
within the 11-km-diameter dacitic Irosin caldera, which was formed more
than 36,000 years ago. A broad, flat moat is located below the prominent
SW caldera rim; the NE rim is buried by the andesitic Bulusan complex.
Bulusan is flanked by several other large intracaldera lava domes and
cones, including the prominent Mount Jormajan lava dome on the SW flank
and Sharp Peak to the NE. The summit of Bulusan volcano is unvegetated
and contains a 300-m wide, 50-m-deep crater. Three small craters are
located on the SE flank. Many moderate explosive eruptions have been
recorded at Bulusan since the mid-19th century.
Sources: Philippine Institute of Volcanology and Seismology
http://www.phivolcs.dost.gov.ph/, Inquirer
http://newsinfo.inq7.net/inquirerheadlines/regions/view_article.php?article_id=29009
Bulusan Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-01=
COLIMA Western México 19.514°N, 103.62°W; summit elev. ~3,850 m
Based on reports from the Mexico City MWO and satellite imagery, the
Washington VAAC reported that an eruption plume from Colima on 29
October reached an altitude of 6.1 km (20,000 ft) a.s.l. and drifted S.
Geologic Summary. The Colima volcanic complex is the most prominent
volcanic center of the western Mexican Volcanic Belt. It consists of two
southward-younging volcanoes, Nevado de Colima (the 4,320 m high point
of the complex) on the N and the historically active Volcán de Colima on
the S. Volcán de Colima (also known as Volcán Fuego) is a youthful
stratovolcano constructed within a 5-km-wide caldera, breached to the S,
that has been the source of large debris avalanches. Major slope
failures have occurred repeatedly from both the Nevado and Colima cones,
and have produced a thick apron of debris-avalanche deposits on three
sides of the complex. Frequent historical eruptions date back to the
16th century. Occasional major explosive eruptions (most recently in
1913) have destroyed the summit and left a deep, steep-sided crater that
was slowly refilled and then overtopped by lava dome growth.
Source: Washington Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/messages.html
Colima Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1401-04=
KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m
Seismic activity increased at Karymsky during 21-27 October, with
350-550 shallow earthquakes occurring daily. Explosions produced ash
plumes that may have reached altitudes of 2.5-5.0 km (8,200-16,400 ft)
a.s.l. and drifted E, NE, and SE. Staff from the Institute of
Volcanology and Seismology (IVS) observed a series of ash bursts that
produced plumes to 2.0 km (6,600 ft) a.s.l. on 25 October. A thermal
anomaly in the crater was detected on satellite imagery during 19-24
October.
Geologic Summary. Karymsky, the most active volcano of Kamchatka's
eastern volcanic zone, is a symmetrical stratovolcano constructed within
a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago.
Construction of the Karymsky stratovolcano began about 2,000 years
later. The latest eruptive period began about 500 years ago, following a
2,300-year quiescence. Much of the cone is mantled by lava flows less
than 200 years old. Historical eruptions have been Vulcanian or
Vulcanian-Strombolian with moderate explosive activity and occasional
lava flows from the summit crater. Most seismicity preceding Karymsky
eruptions has originated beneath Akademia Nauk caldera, which is located
immediately S of Karymsky volcano and erupted simultaneously with
Karymsky in 1996.
Source: Kamchatkan Volcanic Eruption Response Team
http://www.kscnet.ru/ivs/kvert/updates.shtml
Karymsky Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-13=
KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m
The summit of Kilauea continued to slowly inflate S of Halema'uma'u
caldera during 25-31 October. Incandescence was intermittently but
strongly visible from the East Pond and January vents, and occasionally
dimly visible from South Wall complex and Drainhole vent in Pu'u 'O'o's
crater. Lava from the Campout and PKK systems continued to flow off of a
lava delta into the ocean at the East Lae'apuki and East Ka'ili'ili
entries. On 25 October, two separate break-out lava flows were visible
on Pulama pali. The upper flow at about 320 m (1,050 ft) elevation
consisted of ‘a’a and pahoehoe and the lower flow at 114 m (375 ft) was
solely pahoehoe.
Geologic Summary. Kilauea, one of five coalescing volcanoes that
comprise the island of Hawaii, is one of the world’s most active
volcanoes. Eruptions at Kilauea originate primarily from the summit
caldera or along one of the lengthy E and SW rift zones that extend from
the caldera to the sea. About 90% of the surface of Kilauea is formed by
lava flows less than about 1,100 years old; 70% of the volcano's surface
is younger than 600 years. The latest Kilauea eruption began in January
1983 along the E rift zone. This long-term ongoing eruption from Pu`u
`O`o-Kupaianaha has produced lava flows that have traveled 11-12 km from
the vents to the sea, paving broad areas on the S flank of Kilauea and
adding new land beyond the former coastline.
Source: US Geological Survey Hawaiian Volcano Observatory
http://volcano.wr.usgs.gov/hvostatus.php
Kilauea information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01-
LANGILA New Britain Island, Papua New Guinea 5.53°S, 148.42°E; summit
elev. 1,330 m
During 23-31 October, eruptive activity at Langila’s Crater 2 consisted
of continuous emissions of gray-to-brown ash plumes accompanied by
sub-forceful gray ash plumes. Pilots reported plumes to an altitude of
2.4 km (8,000 ft) a.s.l. that drifted NE. Explosions of incandescent
lava fragments were visible during 23-30 October. Based on satellite
imagery, the Darwin VAAC reported that on 31 October a small ash plume
rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted NNE.
Geologic Summary. Langila, one of the most active volcanoes of New
Britain, consists of a group of four small overlapping composite cones
on the lower eastern flank of the extinct Talawe volcano. Talawe is the
highest volcano in the Cape Gloucester area of NW New Britain. A
rectangular, 2.5-km-long crater is breached widely to the SE; Langila
volcano was constructed NE of the breached crater of Talawe. An
extensive lava field reaches the coast on the N and NE sides of Langila.
Frequent mild-to-moderate explosive eruptions, sometimes accompanied by
lava flows, have been recorded since the 19th century from three active
craters at the summit of Langila. The youngest and smallest crater (no.
3 crater) was formed in 1960 and has a diameter of 150 m.
Sources: Herman Patia, Rabaul Volcano Observatory,
Darwin Volcanic Ash Advisory Centre
http://www.bom.gov.au/info/vaac/advisories.shtml
Langila Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-01=
RABAUL New Britain Island, Papua New Guinea 4.271°S, 152.203°E; summit
elev. 688 m
Based on satellite imagery, the Darwin VAAC reported that a small
ash-and-steam plume from Rabaul reached an altitude of 3.0 km (10,000
ft) a.s.l. and drifted NW on 26, 27, and 28 October. The RVO reported
that mild eruptions during 29-30 October produced thick, gray ash plumes
that drifted N and NW. Fine ashfall was reported from Namanula,
including surrounding areas downwind, and E Rabaul town. Seismicity was
at background levels and the rate of ground deformation was low.
Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle
Peninsula at the NE end of New Britain forms a broad sheltered harbor.
The outer flanks of the 688-m-high asymmetrical pyroclastic shield
volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km
caldera is widely breached on the E, where its floor is flooded by
Blanche Bay. Two major Holocene caldera-forming eruptions at Rabaul took
place as recently as 3,500 and 1,400 years ago. Three small
stratovolcanoes lie outside the northern and NE caldera rims.
Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on
the caldera floor near the NE and western caldera walls. Several of
these, including Vulcan cone, which was formed during a large eruption
in 1878, have produced major explosive activity during historical time.
A powerful explosive eruption in 1994 occurred simultaneously from
Vulcan and Tavurvur volcanoes and forced the temporary abandonment of
Rabaul city.
Sources: Herman Patia, Rabaul Volcano Observatory,
Darwin Volcanic Ash Advisory Centre
http://www.bom.gov.au/info/vaac/advisories.shtml
Rabaul Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-14=
SAKURA-JIMA Kyushu, Japan 31.58°N, 130.67°E; summit elev. 1,117 m
Based on information from JMA, the Tokyo VAAC reported that on 25 and 27
October, ash plumes from Sakura-jima reached altitudes of 2.1-2.4 km
(7,000-8,000 ft) a.s.l. Plumes drifted SW and NE, respectively.
Geologic Summary. Sakura-jima, one of Japan's most active volcanoes, is
a post-caldera cone of the Aira caldera at the northern half of
Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow was
associated with the formation of the 17 x 23-km-wide Aira caldera about
22,000 years ago. The construction of Sakura-jima began about 13,000
years ago and built an island that was finally joined to the Osumi
Peninsula during the major explosive and effusive eruption of 1914.
Activity at the Kita-dake summit cone ended about 4,850 years ago, after
which eruptions took place at Minami-dake. Frequent historical
eruptions, recorded since the 8th century, have deposited ash on
Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay
only 8 km from the summit. The largest historical eruption took place
during 1471-76.
Source: Tokyo Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
Sakura-jima Information from the Global Volcanism Program
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=0802-08=
SANTA MARÍA Guatemala 14.756°N, 91.552°W; summit elev. 3,772 m
According to the Washington VAAC, minor emissions from Santa María's
Santiaguito lava-dome complex on 26, 27, and 30 October were visible on
satellite imagery. The small plumes of gas and light ash drifted
predominantly W.
Geologic Summary. Symmetrical, forest-covered Santa María volcano is one
of a chain of large stratovolcanoes that rises dramatically above the
Pacific coastal plain of Guatemala. The stratovolcano has a
sharp-topped, conical profile that is cut on the SW flank by a large,
1-km-wide crater, which formed during a catastrophic eruption in 1902
and extends from just below the summit to the lower flank. The renowned
Plinian eruption of 1902 followed a long repose period and devastated
much of SW Guatemala. The large dacitic Santiaguito lava-dome complex
has been growing at the base of the 1902 crater since 1922. Compound
dome growth at Santiaguito has occurred episodically from four
westward-younging vents, accompanied by almost continuous minor
explosions and periodic lava extrusion, larger explosions, pyroclastic
flows, and lahars.
Source: Washington Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/messages.html
Santa María Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-03=
SEMERU Java, Indonesia 8.11°S, 112.92°E; summit elev. 3,676 m
Based on a pilot report, the Darwin VAAC reported that on 25 and 26
October, an eruption plume from Semeru reached 7.6 km (25,000 ft) a.s.l.
and drifted W. On 30 October, ash-and-steam emissions were detected on
satellite imagery.
Geologic Summary. Semeru is the highest volcano on Java and one of its
most active. The symmetrical stratovolcano rises abruptly to 3,676 m
above coastal plains to the S and lies at the southern end of a volcanic
massif extending N to the Tengger caldera. Semeru has been in almost
continuous eruption since 1967. Frequent small-to-moderate Vulcanian
eruptions have accompanied intermittent lava dome extrusion, and
periodic pyroclastic flows and lahars have damaged villages below the
volcano. A major secondary lahar on 14 May 1981 caused more than 250
deaths and damaged 16 villages.
Source: Darwin Volcanic Ash Advisory Centre
http://www.bom.gov.au/info/vaac/advisories.shtml
Semeru Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-30=
SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev.
1,052 m
During 20-27 October, lava-dome growth at Soufrière Hills continued and
was concentrated on the NE part of the edifice. Rockfalls and small
pyroclastic flows originating from the active lobe traveled down the NE
flank. Several small stubby spine-like structures were observed on the
SE summit region of the dome.
Based on information from the MVO, satellite imagery, and the Piarco
MWO, the Washington VAAC reported that continuous ash and gas emissions
during 25-31 October produced plumes that drifted NW and W. Plumes
reached altitudes of 2.1 km (7,000 ft) a.s.l. A hotspot was detected on
satellite imagery during 25-27 October and 29 October.
Geologic Summary. The complex, dominantly andesitic Soufrière Hills
volcano occupies the southern half of the island of Montserrat. The
summit area consists primarily of a series of lava domes emplaced along
an ESE-trending zone. English's Crater, a 1-km-wide crater breached
widely to the east, was formed during an eruption about 4000 years ago
in which the summit collapsed, producing a large submarine debris
avalanche. Block-and-ash flow and surge deposits associated with dome
growth predominate in flank deposits at Soufrière Hills. Non-eruptive
seismic swarms occurred at 30-year intervals in the 20th century, but
with the exception of a 17th-century eruption that produced the Castle
Peak lava dome, no historical eruptions were recorded on Montserrat
until 1995. Long-term small-to-moderate ash eruptions beginning in that
year were later accompanied by lava-dome growth and pyroclastic flows
that forced evacuation of the southern half of the island and ultimately
destroyed the capital city of Plymouth, causing major social and
economic disruption.
Sources: Montserrat Volcano Observatory http://www.mvo.ms/,
Washington Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/messages.html
Soufrière Hills Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1600-05=
ST. HELENS Washington, USA 46.20°N, 122.18°W; summit elev. 2,549 m
During 25-31 October, the lava dome at Mount St. Helens continued to
grow and produce small rockfalls. On 29 October, a M 3.2 earthquake was
accompanied by a rockfall that produced a small plume. The plume filled
the crater to just above the rim and quickly dissipated.
Geologic Summary. Prior to 1980, Mount St. Helens formed a conical,
youthful volcano sometimes known as the Fuji-san of America. During the
1980 eruption the upper 400 m of the summit was removed by slope
failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially
filled by a lava dome. Mount St. Helens was formed during nine eruptive
periods beginning about 40-50,000 years ago, and has been the most
active volcano in the Cascade Range during the Holocene. The modern
edifice was constructed during the last 2,200 years, when the volcano
produced basaltic as well as andesitic and dacitic products from summit
and flank vents. Historical eruptions in the 19th century originated
from the Goat Rocks area on the N flank, and were witnessed by early
settlers.
Source: US Geological Survey Cascades Volcano Observatory
http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity/framework.html
St. Helens Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05-
SULU RANGE New Britain Island, Papua New Guinea 5.50°S, 150.942°E
The RVO reported that during 28 September-24 October, seismic activity
in the Sulu Range declined. Vapor plumes that were emitted from the
Silanga Hotsprings were visible about 20 km NE from Bialla. A moderately
strong sulfur smell from the Silanga and Talopu hot springs continued to
be reported.
Geologic Summary. The Sulu Range consists of a group of partially
overlapping small stratovolcanoes in west-central New Britain off
Bangula Bay. The 610-m Mount Malopu forms the high point of the
basaltic-to-rhyolitic complex at its SW end. Lava Point forms a
peninsula extending about 1 km into Bangula Bay at the NW side of the
Sulu Range. The Walo hydrothermal area, consisting of solfataras and mud
pots, lies on the coastal plain west of the SW base of the Sulu Range.
Prior to 2006, no historical eruptions had occurred from the Sulu Range,
although some of the cones display a relatively undissected morphology.
Source: Herman Patia, Rabaul Volcano Observatory
Sulu Range Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-09=
SUWANOSE-JIMA Ryukyu Islands, Japan 29.53°N, 129.72°E; summit elev. 799 m
Based on information from JMA, the Tokyo VAAC reported that on 27 and 28
October, ash plumes from Suwanose-jima reached altitudes of 1.8 km
(6,000 ft) a.s.l. Plumes drifted E on 28 October.
Geologic Summary. The 8-km-long, spindle-shaped island of Suwanose-jima
in the northern Ryukyu Islands consists of an andesitic stratovolcano
with two historically active summit craters. Only about 50 persons live
on the sparsely populated island. The summit of the volcano is truncated
by a large breached crater extending to the sea on the E flank that was
formed by edifice collapse. Suwanose-jima, one of Japan’s most
frequently active volcanoes, was in a state of intermittent strombolian
activity from On-take, the NE summit crater, that began in 1949 and
lasted nearly a half century. The largest historical eruption took place
in 1813-14, when thick scoria deposits blanketed residential areas,
after which the island was uninhabited for around 70 years. The SW
crater produced lava flows that reached the western coast in 1813, and
lava flows reached the eastern coast of the island in 1884.
Source: Tokyo Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
Suwanose-jima Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0802-03=
TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m
IG reported that during 25-30 October emissions from Tungurahua produced
plumes consisting of steam, gas, and moderate ash that reached altitudes
of 7-8 km (23,000-26,000 ft) a.s.l. and drifted W, SW, NW, and NE.
Ashfall was reported from several towns downwind of the plumes including
Penipe (8 km SW), Bilbao (8 km W), Cotaló (13 km NM), and Baños (8 km
NNE). On 28 October, incandescent blocks were expelled from the summit
and rolled about 500 m down the W and E flanks. The next day, a lahar
traveled NNW down the Mandur drainage and muddy water swelled in the
Vazcún drainage.
Geologic Summary. The steep-sided Tungurahua stratovolcano towers more
than 3 km above its northern base. It sits ~140 km S of Quito, Ecuador’s
capital city, and is one of Ecuador's most active volcanoes. Historical
eruptions have been restricted to the summit crater. They have been
accompanied by strong explosions and sometimes by pyroclastic flows and
lava flows that reached populated areas at the volcano's base. The last
major eruption took place from 1916 to 1918, although minor activity
continued until 1925. The latest eruption began in October 1999 and
prompted temporary evacuation of the town of Baños on the N side of the
volcano.
Source: Instituto Geofísico-Escuela Poltécnica Nacional
http://www.igepn.edu.ec/vulcanologia/tungurahua/actividad/informet.htm
Tungurahua Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08=
UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m
Based on pilot reports, the Buenos Aires VAAC reported continuous
emissions from Ubinas on 25, 27-28, and 30-31 October. The plumes rose
to 5.5-8.5 km (18,000-28,000 ft) a.s.l. and drifted N, NW, SW, and W.
Geologic Summary. A small, 1.2-km-wide caldera that cuts the top of
Ubinas, Peru's most active volcano, gives it a truncated appearance.
Ubinas is the northernmost of three young volcanoes located along a
regional structural lineament about 50 km behind the main volcanic front
of Peru. The upper slopes of the stratovolcano, composed primarily of
Pleistocene andesitic lava flows, steepen to nearly 45 degrees. The
steep-walled, 150-m-deep summit caldera contains an ash cone with a
500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche
deposits from the collapse of the SE flank of Ubinas extend 10 km from
the volcano. Widespread plinian pumice-fall deposits from Ubinas include
some of Holocene age. Holocene lava flows are visible on the volcano's
flanks, but historical activity, documented since the 16th century, has
consisted of intermittent minor explosive eruptions.
Source: Buenos Aires Volcanic Ash Advisory Center
http://www.bom.gov.au/products/Volc_ash_recent.shtml
Ubinas Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1504-02
**+++++++++++++++++++++++++++++++++++++**
**Sally Kuhn Sennert**
**Global Volcanism Program**
Smithsonian Institution
National Museum of Natural History MRC-119
Department of Mineral Sciences
Washington, D.C., 20560
http://www.volcano.si.edu/reports/usgs/index.cfm
Phone: 202.633.1805
Fax: 202.357.2476
<http://www.volcano.si.edu/reports/usgs/>++++++++++++++++++++++++++++++++++++++++++
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